Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION:
Axle Booster
FIELD OF THE INVENTION
The present invention relates to an axle booster used by
trailers that carry indivisible heavy loads.
BACKGROUND OF THE INVENTION
There are laws relating to the weight of loads that can
be carried on ou:r highways. These load laws are expressed in
terms of load upon each axle group. Most heavy loads are
capable of being divided into smaller loads in order to comply
with these laws. However, some loads are unitary structures
that are indivis:ible. In order to comply with load laws when
hauling indivisible heavy loads additional axles groups must
be added. These additional axle groups are commonly known as
"axle boosters".
The theory behind an axle booster, is that an indivisible
heavy load can be carried within the limits set by the load
laws, if the load can be spread over sufficient additional axle
groups. The axle booster consists of a first frame and a second
frame. The first frame has a front end and a rear end. At
least one axle, preferably two axles, is secured toward the
rear end of the first frame. The second frame has a front end
and a rear end. A coupling is positioned at the front end of
the second frame, which is used to attach the axle booster to
a trailer bearinq the indivisible heavy load. The second frame
is pivotally connected to the first frame by a pivotal
connection. The pivotal connection is positioned adjacent to
the coupling of the second frame and at the front end of the
first frame, with the rear end of the second frame overlying
the front end of the first frame. The pivotal connection
serves as a fulcx-um and the rear end of the second frame serves
as a lever. A selective distribution of load from the trailer
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to the axle booster is effected by exerting a lifting force
upon the rear end of the second frame. This serves to lift the
end of the trailer and transfer a portion of the weight onto
the axle booster. A plurality of air bags are positioned
between the first. frame and the rear end of the second frame
to exert the lift required to the transfer of weight.
Axle boosters, as described above, operated for a number
of years when manual valves were used to inflate the air bags.
Problems are occurring, however, now that the industry has
started to shift to automatic inflation through height control
valves running from the trailer unit. Automatic height control
valves vary the inflation pressure in the air bags to maintain
the trailer deck at a preset height. The trailer deck is at
a constant height whether loaded or unloaded. As load is added
to the trailer, the automatic height control valves increase
the air pressure to the air bags. When the axle booster is
connected to the automatic height control system of the
trailer, the airloags of the axle booster receive the same air
pressure as the a.ir bags of the trailer. Current axle booster
configurations are not working properly with the automatic
height controls due to mechanical inefficiencies inherent in
the design the axle boosters. The automatic systems are
incapable of transferring sufficient weight to the axle
boosters. In order to compensate additional air bags are being
added, but this is not completely solving the problem.
Shimming is also being used, but this also is not completely
solving the problem either. As a result, the vast majority of
trailers with ax:1e boosters operating with automatic height
controls for air:bag inflation are not in compliance with load
laws.
SUNKARY OF THE INVENTION
What is required is a configuration of axle booster that
is compatible with automatic height control systems for air bag
inflation.
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According tc> the present invention there is provided an
axle booster consists of a first frame and a second frame. The
first frame has a front end and a rear end. At least one axle
is secured toward the rear end of the first frame whereby
support wheels are rotatably mounted to the first frame. The
second frame has a front end and a rear end. A coupling is
positioned at the front end of the second frame, whereby the
second frame is attached to a trailer. The rear end of the
second frame is pivotally connected to the first frame by a
pivotal connection. The pivotal connection is spaced forward
of the least one axle of the first frame, with the front end
of the first frame overlying the second frame. A plurality of
air bags are positioned between the second frame and the front
end of the first frame. Upon inflation of the air bags a
lifting force is exerted upon a rear of the trailer to
selectively trans-fer weight from the trailer to the at least
one axle of the first frame.
The axle booster, as described above, has proven to be
more readily adaptable for use with automated air bag inflation
systems incorporated into the trailer's automatic inflation
height control. Of course, the axle booster can also be used
with manual air bag inflation controls as is necessary for use
with a trailer that is not equipped with an air suspension
system. Improve<i mechanical advantage has been obtained by
changing the relative positioning of the first frame and the
second frame, changing the position of the pivotal connection
and changing the position of the air bags, as will hereinafter
be further described.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more
apparent from the following description in which reference is
made to the appencied drawings, the drawings are for the purpose
of illustration only and are not intended to in any way limit
the scope of the invention to the particular embodiment or
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embodiments shown., wherein:
FIGURE 1 is a side elevation view of an axle booster
constructed in accordance with the teachings of the present
invention, with air bags in an intermediate position.
FIGURE 2 is a side elevation view of the axle booster
illustrated in FIGURE 1, with air bags substantially deflated.
FIGURE 3 is a side elevation view of the axle booster
illustrated in FIGURE 1, with air bags substantially inflated
with a trailer not bearing a load.
FIGURE 4 is a side elevation view of the axle booster
illustrated in FIGURE 1, with air bags substantially inflated
with a trailer bearing a load.
FIGURE 5 is a top plan view of the axle booster
illustrated in FIGURE 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment, an axle booster generally
identified by reference numeral 10, will now be described with
reference to FIGURES 1 through S.
Structure and Relationship of Parts:
Referring to FIGURE 1, axle booster 10 consists of a first
frame 12 and a second frame 14. First frame 12 has a front end
16 and a rear end. 18. Second frame 14 has a front end 20 and
a rear end 22. A pair of axles 24 and 25 are secured
transversely in parallel spaced relation to rear end 18 of
first frame 12. Axles 24 and 25 support rotatably mounted
wheels 26. A coupling, generally indicated by reference
numeral 28 is positioned at front end 20 of second frame 14.
Coupling 28 is used to attached second frame 14 to a trailer.
Coupling 28 is known in the art and does not form part of the
present invention. The particular form of coupling 28 will vary
with the style of trailer. The form of coupling 28 chosen for
the purpose of illustration has a locking jaw 30 with a fixed
jaw member 32 and a second jaw member 34. Coupling 28 also has
an extending weight transfer arm 36 terminating in a pressure
member 38. Rear end 22 of second frame 14 is pivotally
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connected to first frame 12 by a pivotal connection identified
by reference numeral 40. Pivotal connection 40 is spaced from
axle 24 of first frame 12. It is to be noted that in marked
contrast to the prior art front end 16 of first frame 12
5 overlies second frame 14. Referring to FIGURE 1, a plurality
of air bags 42 are positioned between second frame 14 and front
end 16 of first frame 12. Upon inflation of air bags 42 a
lifting force is exerted, which is used to selectively transfer
weight from a trailer to axle booster 10 as will hereinafter
be further described in relation to operation.
Operation:
The use and operation of axle booster 10 will now be
described with reference to FIGURES 1 through 5. Coupling 28
of axle booster 10, as illustrated in FIGURE 1, is intended to
be used with a -style of trailer commonly used to transport
construction vehicles. Referring to FIGURE 2, there is
illustrated a rear portion 102 of a trailer 100. Rear portion
102 of trailer 100 has a transverse coupling bar 104 and a
sloped loading ramp 106. When an indivisible load is to be
carried upon trai:ler 100, axle booster 10 is coupled to trailer
100 with air bags 42 in a deflated condition. In order to do
this locking jaw 30 is attached to transverse coupling bar 104.
Pressure member :38 of weight transfer arm 36 bears against
sloped loading ramp 106. Referring to FIGURES 3 and 4, air
bags 42 are then inflated. The inflation of air bags 42 can
be performed through a manually activated valve or through an
air coupling to an automated height adjustment system for
trailer 100. Referring to FIGURE 3 and 4, an air conduit 108
is shown as extending from trailer 100. Air conduit 108 links
axle booster 10 'to an automated height adjustment system of
trailer 100. As air bags 42 inflate, locking jaw 30 exerts an
upward force upo:n transverse coupling bar 104 and pressure
member 38 bears against sloped loading ramp 106. As can be
seen from a comparison of FIGURES 2, 3 and 4, as air bags 42
continue to inflate rear portion 102 of trailer 100 is
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physically lifted. When trailer 100 is not bearing a load,
rear portion 102 is lift right off the ground, as is
illustrated in FIGURE 3. Referring to FIGURE 4, when trailer
100 is bearing a:Load, rear portion 102 is lifted sufficiently
to raise the height of the trailer deck and shift a portion of
the rear load to axles 24 and 25 of axle booster 10. It is to
be noted that the lifting action results in some pivotal
movement of first frame 12 at trunnion 41. It also results in
a portion of the weight being transferred from rear portion 102
of trailer 100 tovvard the front, as will hereinafter be further
explained.
Cautionary iti'arnings :
Care must be taken in positioning pivotal connection 40
along first frame 12. On a dual axle trailer, if pivotal
connection 40 were positioned to provide the maximum mechanical
advantage, pivotal connection 40 would be positioned at
trunnion 41. However, this positioning is not practical due
to the limited travel in air bags 42. Each of air bags 42 has
a limited working range. Although air bags 42 are capable of
travel beyond their working range, they are only capable of
providing a lifting force within their working range. The
precise positioning of pivotal connection 40 is, therefore, a
compromise intended to obtain the maximum mechanical advantage
within the working range of air bags 42. The flexing of
trailer 100 must be taken into account. Air bags 42 will need
to inflate axle booster 10 sufficiently to accommodate flexing
by trailer 100 before any actual lift can provided by axle
booster 10 to trailer 100. When axle booster 10 is first
attached to trailer 100, air bags 42 receive the same air
pressure as the air bags of trailer 100. This results in an
initial lift of rear portion 102 of trailer 100. If trailer
100 were without load, the lift would be enough to lift rear
portion 102 of trailer 100 right off the ground. When trailer
100 is under heavy load, rear portion 102 is raised
sufficiently to alter the height of the trailer deck. In
response to the raising of the height of the trailer deck, the
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automatic height control will make an adjustment to reduce air
pressure to all air bags to maintain the height of the trailer
deck at the preset height. While the addition of the axle
booster has the effect of taking some of the weight off the
rear axles of trailer 100, the lifting of rear portion 102 of
trailer 100 also has the effect of shifting a portion of the
weight toward the front. In view of this shift of weight
toward the front, in order to achieve maximum loading it is
necessary to position the load rearward on trailer 100 when
axle booster 10 is to be added. The best positioning for the
load on trailer 1.00 without axle booster 10 will differ from
the best positioning of the load on trailer 100 with axle
booster 10.
In this patent document, the word "comprising" is used in
its non-limiting sense to mean that items following the word
are included, but items not specifically mentioned are not
excluded. A refe:rence to an element by the indefinite article
"a" does not exclude the possibility that more than one of the
element is preserit, unless the context clearly requires that
there be one and only one of the elements. It will be apparent
to one skilled in the art that modifications may be made to the
illustrated embodiment without departing from the spirit and
scope of the invention as hereinafter defined in the Claims.
